Annex 2.C Vulnerability of roof coverings
This annex provides guidance on the vulnerability of roof coverings and is concerned with the performance of roofs when exposed to fire from neighbouring buildings.
Commission Decision 2005/823/EC amending Decision 2001/671/EC establishing a classification system for the external fire performance of roofs and roof coverings allows the classification of performance by either:
BS 476: Part 3: 2004 (National Test), External fire exposure roof tests, or
BS EN 13501-5: 2005 (European Test), Fire classification of construction products and building elements, Part 5 - Classification using test data from external fire exposure to roof tests.
The level of vulnerability is established from the guidance to Standard 2.1 to 2.15. Reference throughout this document to a low, medium or high vulnerability, will be satisfied by following the guidance in the table below. The British Standard classification does not automatically equate with the equivalent classifications in the European standards column, therefore products cannot typically assume a European class, unless they have been tested accordingly. The designer is free to choose materials or products, which satisfy either the British Standard Tests or the Harmonised European Tests.
Transitional period - British and European fire tests will co-exist in use until the British Standard classifications are withdrawn.
The national test for roof coverings is BS 476: Part 3: 2004 which measures the capability of a roof to resist penetration from fire and flame spread when the external surface is exposed to radiation and flames.
BS 476: Part 3: 2004 sets out a classification system based on external penetration and flame spread as set out in the following table. The first letter of the designation indicates fire penetration performance i.e. the time at which any glowing or flaming [other than that from the gas pilot flame] appears on the underside of the specimen. The second letter of the designation indicates flame spread performance. The addition of the suffix ‘X’ indicates dripping from the underside of the specimen, any mechanical failure or development of holes in the specimen. The angle of the specimen in the test is designated by the prefix ’S’ [slope] or ‘F’ [flat].
Table 2.9. Roof Coverings: Penetration from fire and flame spread
The European test method has been published as DD ENV 1187: 2002, ‘Test methods for external fire exposure to roofs’, which specifies four methods for determining the performance of roofs to external fire exposure:
Test 1 : with burning brands
Test 2 : with burning brands and wind
Test 3 : with burning brands, wind and supplementary radiant heat
Test 4 : two stage test method incorporating burning brands, wind and supplementary radiant heat.
Only test method 4 evaluates penetrability in a satisfactory way to satisfy the fire performance requirements in the United Kingdom. For this reason, (t4) has been added to the European test designations to add clarity.
The performance criteria in terms of vulnerability to external fire exposure can be satisfied where the roof covering follows the guidance in the following table. The classification methodology is contained in BS EN 13501-5: 2005.
Table 2.10. Classification for roofs / roof coverings exposed to external fire
|Classification for roofs / roof coverings exposed to external fire|
Table 2.11. Vulnerability of roof coverings
|Vulnerability||British Standards||European Standards|
||The material has achieved a classification of Broof(t4) in accordance with BS EN 13501-5: 2005 when tested to DD ENV 1187: 2002 + A1:2005, test 4.|
||The material has achieved a classification of Croof(t4) and Droof(t4) in accordance with BS EN 13501-5: 2005 when tested to DD ENV 1187: 2002 + A1:2005, test 4.|
|High||Any designation other than low or medium vulnerability, including for example, timber shingles or thatch.||The material has achieved a classification of Eroof(t4) and Froof(t4) in accordance with BS EN 13501-5: 2005 when tested to DD ENV 1187: 2002 + A1:2005, test 4.|